"The smartphones going into the world's next two billion pairs of hands may not belong to either Google or Apple, but to Mozilla. The Mozilla Foundation, which oversees open source software projects like the Firefox Web browser, expects to release a mobile operating system for smartphones early next year. Its target market is Latin America, then the rest of the developing world, where smartphones from Apple and Google are still too expensive for most people." Let's hope so, because at the rate things are currently going, we'll end up with like 90% Android, 9% iOS, and 1% other stuff. Who wants that?

Hmm stick to the truth, that might be true for AOT (ahead of time) compiled JS, but you'd have to modify your JS code slightly to make that happen. Highly dynamic languages like JS don't compile very well. FirefoxOS will not run anything like that. It will run Mozillas JS engine and it nowhere near as fast as compiled C or just in time compiled Java. Cold hard truth.

Java is statically typed and the bytecode takes advantage of that. Also, Android uses Dalvik, which has a completely different bytecode, designed for faster interpretation. E.g. it's register-based rather than stack-based.
Not that bytecode interpretation speed matters much, as both Dalvik and Gecko have JITs. But it's a lot easier to make Java code go fast than it's for JS code.